Add PCB thickening with vinyl

content/04_pcb_milling.md

@@ -44,3 +44,9 @@ Here are both boards next to each other; lead-free on top, leaded below.
 
 Looking forward to programming these programmers!
 
+### Thickening
+
+Our PCBs are a bit thinner than the spec for USB connectors. So I cut out the profile on the vinyl cutter and stuck 8 layers on the bottom of my boards. This makes them stick in USB ports much more firmly.
+
+![](/img/04_vinyl_bottom.jpg#c)
+